Geology studies Earth's solid surface through mineralogy, geodesy, and stratigraphy. Earth's rocks are composed of minerals with fixed chemical compositions. Geochemistry analyzes composition of sedimentary, igneous, and metamorphic rocks
Magnetic field generated in fluid outer core by self-exciting dynamo process. Field varies on scales from low to high frequency variations. Main field approximated by dipole tilted 10° to Earth's rotation axis
Geophysics studies Earth's physical processes and properties using quantitative methods. Modern definition includes water cycle, fluid dynamics, and planetary physics. Discipline emerged in 19th century from intersection of multiple sciences
Earthquake warning systems use accelerometers, seismometers and computers to notify regions. Earthquakes occur when stored elastic strain energy is released along faults. Pressure waves travel faster than shear waves, with destructive effects reaching 8-story buildings
Gravimetry measures the strength of gravitational fields. Gravity is measured in units of acceleration, typically m/s². Every mass has an associated gravitational potential
Mantle is a layer of silicate rock between crust and outer core. Makes up 67% of Earth's mass and 46% of its radius. Thickness is 2,900 kilometers, with 84% of Earth's volume. Behaves as viscous fluid on geologic time scales